There is family aggregation of obstructive sleep apnea (OSA) as has been shown in the United States, Europe and recently in Iceland. Iceland represents a unique opportunity for genetic research. It is a community that was settled by founders in the 9 th Century, and has developed in relative isolation since that time to its present size of 285,000 persons. Moreover, there is a commitment to record keeping that has allowed deCODE Genetics, who are collaborators on this grant, to develop a computerized genealogy data base that permits the ancestry of individuals to be traced over centuries. This tool, together with the founder nature of the population, makes possible a unique genealogy-driven approach to study the genetics of complex disorders, an approach that has already been successful.